I've been trying to come up with some sort of pneumatic mine for ages. It had to be small, cheap, easy to build, and the most challenging- it had to have a delay.

So I came up with this and finished it today. It cost $10 and wasn't really hard to build. Best of all, it actually works as intended!

It consists of a 2" plug and a 2" x 1/2" bushing glued into a coupling.A short length of 1/2" pipe runs through the bushing to the inside of the chamber and is capped. The cap has a pin-hole through it. The pipe extends out of the large bushing into a 1/2" x 3/4" bushing which connects to a 3/4" union.

The idea is simple. You fill the mine through the schrader valve and it fills up. Slowly, air bleeds into the small 1/2" chamber until it ruptures a burst disc, thus firing some baby powder or whatever you put in it.

It does work, but I'm still experimenting with burst discs to find the balance between power and an appropriate delay.

For triggered actuation, you should try threading a long hook through the end of the main chamber and into the pin hole. Pressurize, unscrew a couple times, and it would start to let air into the smaller chamber. I mgiht have to try a couple of these. Glad you finally figured a simple design out.

Try 1/16" rubber, it bursts at exactly 80 psi, how high do you pressurize it? Also, with the hook, you could have like six hanging down from your belt and/or various pockets, like in all the shoot-em-up movies.

So the rubber would be pretty good, it's only $3 for a square foot, so you could get around 30 discs. See if you can get it at a local hardware store.

I'm going to make a couple of these, and experiment with diferent burst discs, different pin hole sizes for different times, etc. They could help with freaking people out on Halloween, considering how short the "barrel" is and all burst discs are frickin loud anyway. See someone coming up the street, pop in the rigth disc for the right time delay, load it up with flour, pressurize, and stuff it in a bush or something.

Another question, forget the variables, about how long does it take for the disc to rupture? Aluminum Foil: ? secondsSoda Bottle: ? secondsMilk Jug: ? secondsAnd whatever else you use for discs.